This subject matter disclosed herein relates to a fuel cell system provided for use on board an aircraft and, in particular, to temperature regulation of such a fuel cell system.
Fuel cells generate electrical energy with low emissions and a high level of efficiency. The power generated by an aircraft fuel cell may be utilized to supplement or replace the primary power generation system. An aircraft fuel call may also be utilized for emergency power generation to supplement or replace an aircraft ram air turbine.
Thermal regulation is an important consideration for fuel cells utilized in aircraft emergency power generation systems. Due to the immediate demand for power in an emergency situation, delayed start times caused by a cold fuel cell are unacceptable. If a warming feature is not available for the fuel cell, a supplemental battery system will be necessary to provide power until the fuel cell has warmed to its operational temperature. The use of a battery system is both heavy and expensive.
Conventional fuel cells include an anode region and a cathode region separated by an electrolyte. When the fuel cell is operated, a fuel, for example hydrogen, is supplied to the anode side and an oxygen-containing oxidant, such as air, is supplied to the cathode side. In fuel cells where the electrolyte is a polymer electrolyte membrane (PEM), the hydrogen molecules react at an anode catalyst in the anode region to form positively charged hydrogen ions (H+) and transfer electrons to the electrode. The H+ ions, which are formed in the anode region, then diffuse through the electrolyte to the cathode where they react, at a cathode catalyst, with the oxygen supplied to the cathode and the electrons that are transferred to the cathode by way of an external circuit, forming water.